格构拱结构动力响应评估的改进模态推覆分析法

An Improved Modal Pushover Analysis Procedure for Estimating Seismic Responses of Latticed Arch

摘要:

静力推覆分析方法广泛应用于多高层结构在水平地震作用下的抗震性能评估，但将此方法直接应用于竖向地震作用下结构水平和竖向变形耦合显著的大跨度格构拱结构时，计算精度较差.引入结构静力稳定分析的特征刚度参数，提出了一种改进的模态推覆分析(IMPA)方法，通过第一阶段的模态推覆分析建立基于特征刚度的等效单自由度(ESDOF)体系；将各阶ESDOF的动力时程按振型组合进行第二阶段推覆分析，推导出推覆荷载公式；通过两阶段的推覆分析求解结构整体的动力响应.采用IMPA方法对某大跨度格构拱结构分别在硬土和软土场地若干条竖向地震波激励下的动力响应进行分析，与时程分析方法进行对比，计算结果表明：节点竖向位移和单元最不利应力的变化趋势基本一致，平均误差分别为10.5%和33.2%，计算耗时仅约为时程分析法的25%；随着竖向振型截取阶数的增加，IMPA方法的计算精度也相应提高.

Abstract:

The static pushover analysis (SPA) procedure has been widely applied to the estimate of the nonlinear seismic performance of the multistory structure subjected to horizontal earthquakes. However, SPA could hardly obtain a satisfying result in accuracy when applied to the evaluation of seismic responses of the largespan latticed arch under vertical earthquake ground motions, whose lateral and vertical displacements were coupled. Accordingly, an improved modal pushover analysis (IMPA) procedure was proposed, based on the eigenstiffness, introduced from the static stability analysis of structures. Firstly, equivalent single degree of freedom (ESDOF) system was established based on eigenstiffness by modal pushover analysis for each mode selected. Secondly, the seismic responses of the ESDOFs were solved respectively and combined. Finally, the seismic responses of the structure were obtained by pushover analysis once more according to the load formula derived. The seismic responses of a latticed arch under a series of vertical earthquake waves on firm and soft sites, were obtained by IMPA. Compared with the results given by response history analysis, the node vertical displacements and the most unfavorable stresses of the arch were consistent in distribution, with errors about 10.5% and 33.2% respectively, and 25% computing consumption. Along with the increase in the number of the vertical modes selected of the arch, the accuracy of IMPA could improve.